This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. This application addresses broad Challenge Area (15): 15-NS-102: Translation of Gene Silencing Therapeutics. The proposed challenge set forth in the RFA is to extend the current understanding of the feasibility and safety of RNA interference (RNAi) therapeutics for the treatment of chronic neurological disorders from rodent models of disease to a more clinically relevant species. The current proposal outlines a systematic approach to translate work we, and others, have undertaken to investigate RNAi as a potential therapy for the neurological disorder, Huntington's disease (HD) in cell culture and rodent models and apply these findings to the non-human primate (NHP). The proposed studies are a collaboration between the University of Iowa and the Oregon National Primate Research Center (ONPRC). University of Iowa has experience developing and testing RNAi therapeutics in rodents, while the ONPRC has expertise in stereotaxic delivery of viral vectors to the NHP brain. Also, the ONPRC has methodologies, equipment and personnel in place that can evaluate if application of HTT suppression, or RNAi in general, induces neuropathology or neurological symptoms after delivery of RNAi expression vectors to NHP brain. To date, we have shown efficacy of reducing HTT expression in the rhesus macaque putamen by 45%. This suppression of HTT is not associated with the manifestation of any behavioral abnormalities nor neuropathological changes in the putamen.